Process of preparing fatty amines



Patented Sept. 28, 1954 UNITED STATES PATENT OFFICE 2,690,456 PROCESS OF PREPARING FATTY AMINES Malcolm M. Renfrew and Donald T. Warner, Minneapolis, Minn, assignors to General Mills, Inc., a corporation of Delaware N0 Drawing. Application April 7, 1952, Serial No. 281,051

6 Claims. 1

The present invention relates to a process of preparing fatty amines by the catalytic hydrogenation of fatty nitriles and is particularly concerned with the process which results in high yields of the primary fatty amines.

Fatty amines are commonly made by the reduction of fatty nitriles, the fatty nitriles having been prepared from fatty acids. In the conventional process for the production of fatty amines from fatty nitriles, there is generally a substantial yield of secondary amines along with the desired primary amine. Attempts have been made to increase the relative yield of the primary amines, but in general, these prior methods have left much to be desired. In the first place, these prior attempts have not resulted in a satisfactory yield of the primary amine and in addition the methods which have been proposed have entailed various difiiculties.

.One method of increasing the yield of primary amines is by including a large quantity of ammonia in the reduction reaction mixture. These prior methods frequently employed ammonia in the proportion of from 1 to 2 mols per mol of fatty nitrile. It will be readily apparent that by employing this quantity of ammonia in addition to the hydrogen required for the reduction, it is necessary to operate the reduction vessels at extremely high pressures in order to obtain any reasonable capacity. In the present process, difficulties of this type are overcome.

It is therefore an object of the present invention to provide a novel process of reducing fatty nitriles to fatty amines, which process results in a high proportion of the primary fatty amine being formed in preference to the secondary fatty amine.

The invention involves the reduction of fatty nitriles with a hydrogenation catalyst in the presence of a relatively small quantity of am-- monia and of a relatively small quantity of an organic solvent miscible with the nitrile. It has been found that under these conditions a decided- 1y improved yield of primary amine is obtained as compared with prior processes. In addition, the quantity of ammonia employed is relatively small and accordingly the pressure which may be employed in the hydrogenation vessel may be relatively low. The quantity of ammonia which is employed is preferably less than 1 mol per mol of the fatty nitrile and may be from to mol per mol of nitrile. One-third of one mol of ammonia has been found to be very good in a number of instances.

With these low quantities of ammonia the ammonia pressure may amount to pounds per square inch at -140" C. With this low ammonia pressure satisfactory hydrogenation of the nitriles may be elfected by a total pressure of at least and preferably approximately 200 pounds per square inch on the hydrogenation vessel. This is distinctly of advantage in commercial operation and presents a particular advantage in the design of large-scale batch reactors. It is apparent, however, that higher hydrogenation pressures than the total of 200 pounds per square inch may be employed. Many reactors are available that withstand pressures up to 500 pounds per square inch and more, and accordingly these reactors may be used to ad vantage with the present invention. Obviously these reactors may be used at their maximum pressure capacity or at any satisfactory pressure below the maximum.

A Wide variety of solvents which are miscible with the fatty nitrile may be employed. These preferably are low aliphatic alcohols such as methanol, ethanol, isopropanol, butanol and the like. However, ethers such as dioxane and glycols such as ethylene glycol may be used. Hydrocarbons such as cyclohexane, may also be used; but they are somewhat less effective than. are the solvents which are water-miscible.

The quantity of solvent which is employed may be quite small, usually within the range of /2 to 3%, preferably 1% to 2%, based on the weight of the nitrile. Larger quantities of solvents, for example 10%, may be used, but in general, the excess solvent usually does not represent any advantage. In most instances the quantity of solvent employed is so low that for commercial feasibility it is not necessary that the solvent berecovered, and in addition, the quantity of solvent which remains in the primary amine usually is not enough to impair the utility of the product.

A wide variety of hydrogenation catalysts are suitable for the present invention. The nickel catalysts are preferred because of their low cost. Suitable nickel catalysts include Raney nickel, nickel catalysts obtained by wet reduction methods such as Rufert nickel, supported nickel catalysts obtained by dry reduction such as, for example, nickel on kieselguhr, and the reduced nickel borate catalysts disclosed in the copending application of David E. Terry and Jakob L. Jakobsen, Serial No. 235,384, filed July 5, 1951, for Fatty Amines. Other catalysts, such as cobalt catalysts, as Well as precious metal catalysts, such as ruthenium, platinum and palladium catalysts, may also be employed, but are usually not preferred because of their increased cost.

The process involves the simple admixture of the solvent with the catalyst, and the admixture of the catalyst with the fatty nitrile and the introduction of the ammonia and hydrogen under pressure at a suitable reaction temperature. In general, total pressures of from 150-500 pounds per square inch are adequate. Higher pressures obviously may be employed without departing from the spirit of the invention. The temperatures which may be employed are those which are suitable for the particular catalyst. With most nickel catalysts, temperatures in the range of 110l70 C. preferably 130-150 C. are satisfactory. With the cobalt catalysts, similar temperatures may be employed. With the precious metal catalysts such as platinum and palladium, lower temperatures nearer room temperature may be desirable in order to reduce side reactions. With ruthenium, temperatures of around 130 C. are suitable.

The fatty nitriles which may be reduced by the present invention include those containing from 8 to 22 carbon atoms. These nitriles may be prepared from fatty acids, and the fatty acids which are employed may be the mixed fatty acids of a fat or oil, or any selected fraction thereof, or indeed any individual isolated acid. The acids may be saturated or unsaturated, and the reduction conditions may be conducted so that the original unsaturation of the fatty acid may be preserved if desired. Accordingly, the fatty amines which may be prepared may be either saturated or unsaturated.

Example 1 7.0 grams of a water-wet paste of commercial Raney nickel was washed with absolute ethanol to remove the water. The alcohol-wet paste (containing about 3 g. of ethanol) and 400 g. of commercial stearic nitrile were charged to a 1 liter autoclave. 5.9 g. of ammonia were introduced into the reactor. The total ammonia pressure was 85 pounds per square inch at 124 C. Hydrogen was then introduced to a total pres-- sure of 210 pounds per square inch and the hydrogenation was completed at 210 pounds per square inch and 140 145 C. The catalyst was removed by filtration and an analysis of the resulting product showed 91% primary stearyl amine, 6.2% secondary stearyl amine, and about 2% unreacted nitrile.

For comparison purposes, hydrogenations were conducted in the absence of the ammonia but in the presence of the nitrile-miscible solvent, also in the presence of the ammonia and in the absence of a nitrile-miscible solvent, and also in the absence of both the ammonia and the solvent.

The following experiment was conducted with solvent but in the absence of ammonia.

5.0 grams of a water-wet paste of commercial grade Raney nickel was washed with absolute ethanol to remove the water. The excess ethanol was removed by decantation and the ethanolwet paste (containing about 3 g. of ethanol) was mixed with 265 g. of commercial stearic nitrile. The mixture was charged to a 1 liter autoclave and hydrogenated at a. temperature of about 128 C, and a total pressure of 200 pounds per square inch of hydrogen. The catalyst was removed by filtration, and the resulting product showed 74% primary stearyl amine and 26% of secondary stearyl amine.

This demonstrates that the catalytic quantity of solvent in itself does not produce the desired increase in the yield of the primary stearyl amine.

The following experiment demonstrates that the ammonia itself does not produce the increase in yield which was reported at the beginning of this example.

265 grams of commercial stearic nitrile, 5.0 g. of a water-wet paste of commercial grade Raney nickel, and 6.3 g. of ammonia were charged to a 1 liter autoclave and subjected to a pressure of 300 p. s. i. with hydrogen gas. The hydrogenation of the nitrile was conducted at a temperature of -l43 C. and a total pressure of 250- 300 pounds p. s. 1. until the reduction was complete. After removal of the catalyst, analysis of the product showed 75.2% primary stearyl amine, 21.2% secondary stearyl amine, and 2.7% residue.

Two additional runs were conducted as described immediately above, employing the, same proportions of materials except that 6.5 g. of ammonia were employed. The conditions were' otherwise the same. The results showed 76.1% and 76.4% primary stearyl amine, and 19% and 18.8% secondary stearyl amine, and 4.6% residue in each case. These last results indicate that a small amount of ammonia alone does not produce the desired increase in the yield of the primary stearyl amine.

The following experiment demonstrates the yields obtainable when both the solvent and the ammonia are omitted.

265 grams of stearic nitrile and 5 g. of waterwet commercial Raney nickel were charged to a 1 liter autoclave and the mixture was hydrogenated at about -155 C. at a total pressure of 200 p. s. 1. At the completion of the hydrogenation, the catalyst was removed by filtration. Analysis of the resulting product showed 71.4% primary stearyl amine, 25.4% secondary stearyl amine, and 3.2% residue.

Example 2 7.0 grams of a water-wet paste of commercial Raney nickel was washed with absolute ethanol to remove water. The resulting alcohol wet paste was mixed with 400 g. of commercial stearic nitrile in 7.2 g. of ammonia. The resulting mixture was hydrogenated at a total hydrogen pressure of 200 pounds per square inch and a temperature of 133-144 C. The catalyst was re moved by filtration and the resulting product was shown by analysis to contain 92% primary stearyl amine and 65% secondary stearyl amine, and about 1.5% inert material.

Example 3 400 grams of stearic nitrile, 7.0 g. of waterwet commercial Raney nickel (subsequently washed with alcohol to remove water and the resulting alcohol wet paste mixed with the nitrile), and 7 g. of ammonia were subjected to hydrogenation at about 135-145 C. at 200-220 1). s. 1. pressure. The catalyst was removed by filtration and the analysis of the resulting product showed 92% stearyl amine, about 6% secondary stearyl amine, and about 2% inert material.

Example 4 8 grams of water-wet commercial Raney nickel was washed with absolute methanol, and the methanol wet paste was mixed with 400 g. of commercial stearic nitrile. An additional 4 g. of absolute methanol were added to bring the total quantity of methanol to approximately 8 g. The

mixture was heated to a temperature of 135 C. and ammonia gas was introduced with stirring until the pressure in the vessel was 78 p. s. i. Hydrogen was then introduced into the vessel to a total pressure of 200 p. s. i. and the reduction was completed at a temperature of 134-148 C. and a constant pressure of 200-220 p. s. i. which was maintained by continual itnroduction of hydrogen. The catalyst was removed by filtration and the analysis of the product showed 93.5% primary stearyl amine, and 6.5% secondary stearyl amine.

Example 5 12 grams of the reduced nickel borate catalyst prepared as described in the above referred to Terry et al. application, were suspended in absolute ethanol. When the suspension had set-- tled, the excess alcohol was decanted and the residual alcohol wet paste was mixed with 400 g. of commercial stearic nitrile, and the mixture was charged to a 1 liter autoclave. Ammonia (5.8 g.) Was added and the pressure was 80 p. s. i. at 134 C. Then hydrogen was introduced to a total pressure of 200 p. s. i. and the reduction of the nitrile was carried to completion at a temperature of 135145 C. The catalyst was removed by filtration and an analysis of the product showed 88.8% primary stearyl amine, 8.3% secondary stearyl amine, and about 2% inert material.

Several similar reactions were run in which the alcohol was omitted to show the effect of this solvent.

265 grams of commercial stearic nitrile were mixed with approximately 12 g. of a reduced nickel borate catalyst produced as described in the application of Terry et a1. above referred to. The mixture was charged to a 1 liter rocking autoclave. 6.8 g. of ammonia were added to produce an ammonia pressure of 43 p. s. i. at 70 C. The mixture was then subjected to hydrogenation at a temperature of 125-135 C. and a total pressure of 200-210 p. s. i. The product was filtered and analysis of the resulting product indicated 80.5% primary stearyl amine, 15.1% secondary amine, and some inert material.

A similar reaction employing 265 g. stearic nitrile, 12 g. of reduced nickel borate catalyst, 4.7 g. of ammonia (ammonia pressure 92 p. s. i. at 140 C.) and hydrogenation at 135-145 C. with a total pressure of 200 p. s. i. yielded 78.4% primary stearyl amine, 17.7% secondary amine and about 4% inert material. An additional reaction employing 265 g. stearic nitrile, 12 g. of reduced nicke1 borate catalyst, 4.9 g. of ammonia yielded 76.4% primary stearyl amine, 18.1% secondary stearyl amine, and 5.5% inert material.

A fourth reaction employing 400 g. of stearic nitrile, 12 g. of reduced nickel borate catalyst, 5.6 g. of ammonia, yielded 75.1% primary stearyl amine, 21.7% secondary stearyl amine, and about 3% inert material.

A fifth reaction employing 250 g. of commercial stearic nitrile, 11 g. of reduced nickel borate catalyst, and 3.8 g. of ammonia, resulted in the formation of 76% primary stearyl amine, 20.3% secondary stearyl amine, and about 3% inert material.

Erammle 6 400 grams of commercial stearic nitrile were mixed with 12 g. of reduced nickel borate catalyst. and 12 g. of absolute ethanol. The mixture was charged to an autoclave and 5 g. of ammonia were introduced. The hydrogenation was then carried 6.. out at a total pressure of 200 p. s. i. at a temperature of 135-145 C. The catalyst was removed by filtration. Analysis of the resulting product showed 88.5% primary stearyl amine, 9% secondary stearyl amine, and about 2.5% inert material.

Emample 7 400 grams of the nitriles prepared from crude split brown grease, 12 g. of reduced nickel borate catalyst, and 8 g. of absolute ethanol were charged to a 1 liter autoclave. At a temperature of 120 C. gaseous ammonia was pressed in to a pressure of p. s. i. (7.5 g. of ammonia by weight). The hydrogenation was then carried out at a total pressure of 200 p. s. i. by the continual introduction of hydrogen. When the reduction was complete, the catalyst was removed by filtration. The resulting product showed 90.5% primary fatty amines and 9.4% of residue which was largely secondary fatty amines as indicated by the titration value.

Example 8 400 grams of commercial stearic nitrile, 12 g. of reduced nickel borate catalyst, 8 g. of absolute ethanol were charged to a 1 liter autoclave. At a temperature of C. gaseous ammonia (7 g.) were introduced to a pressure of 85 p. s. i. Pressure was then increased to 200 p. s. i. with hydrogen and the hydrogenation was conducted at a temperature of 128-145 C. When the reduction was complete, the catalyst was removed by filtration. Analysis of the resulting product showed 89% primary stearyl amine, 9.3% secondary stearyl amine, and about 2% inert material.

Example 9 400 grams of commercial tallow nitriles, 12 g. of reduced nickel borate catalyst, 8 g. of absolute ethanol and 8 g. of ammonia were charged to a 1 liter autoclave. The mixture was hydrogenated at 145 C. and 260 p. s. i. total pressure. The catalyst was removed by filtration. Analysis of the product showed 87.5% primary tallow amines and 12.5% secondary tallow amines.

Example 10 400 g. of commercial stearic nitrile, 4 g. of commercial 10% ruthenium on charcoal catalyst, 5.6 g. of absolute ethanol, and 5.4 g. of ammonia were charged to a 1 liter autoclave. The mixture was hydrogenated at a total pressure of 220 p. s. i. and a temperature of 130-143 C. After the reduction was complete, the catalyst was removed by filtration. Analysis of the resulting product showed 90.5% of primary stearyl amine, 9% secondary stearyl amine, and 0.5% inert material.

By Way of comparison, a similar reaction was run in the absence of the ethanol as follows. 265 g. of commercial stearic nitrile, 4.9 g. of commercial 10 ruthenium on charcoal catalyst, and 6.4 g. of ammonia were charged to a 1 liter autoclave. The mixture was hydrogenated at 130-140 C. at 200 p. s. i. total pressure. The catalyst was removed by filtration. Analysis of the resulting product showed 72% primary stearyl amine, 25% secondary stearyl amine, and 3% inert material.

Example 11 400 grams of commercial stearic nitrile, 10.6 g. of reduced nickel borate catalyst, and 8 g. of absolute methanol were charged to a 1 liter autoclave. At a temperature of 130 C. gaseous ammonia (6.0 g.) was introduced with stirring to a pressure of 82 p. s. i. The pressure was then increased to 220 p. s.. i. with'hydrogen and the hydrogenation was carried out at 141-148 C. at 220p. s. i..total pressure. After the hydrogenation was complete, the catalyst was removed by filtration. Analysis of the resulting product indicated 92.5% primary steary1 amine, 6.4% secondary stearyl amine, and about 1 inert material.

Example 12 Example 13 400 grams of commercial stearic nitrile, 10.6 g. of reduced nickel borate catalyst, 8 g. of dioxane, and 6.6 g. of ammonia were charged to a 1 liter autoclave. The mixture was hydrogenated to completion at a total pressure of 210 p. s. i. and a temperature or" 135-145 C. The catalyst was removed by filtration. Analysis of the resulting product showed 91 primary stearyl amine, 8% secondary stearyl amine, and approximately 1% inert material.

Example 14 400 grams of commercial stearic nitrile, 13 g. of reduced nickel borate catalyst, 7.9 g. of ethylene glycol, and 7.2 g. of ammonia were charged to a 1 liter autoclave. The mixture was hydrogenated at 220 p. s. i. total pressure, and 130-155 C. When the hydrogenation was completed, the catalyst was removed by filtration. Analysis of the resulting product showed 91% primary stearyl amine, and approximately 9% secondary stearyl amine.

Example 15 265 grams of the nitriles from crude split brown grease, 13 g. of reduced nickel borate catalyst, 8 g. of absolute ethanol, 4.1 g. of ammonia were charged to a 1 liter autoclave. Hydrogenation was conducted at a total pressure of 220 p. s. i. and a temperature of 145-152 C. Upon completion of the reduction the catalyst was removed by filtration. Analysis of the resulting product showed 87.5% primary fatty amines and 12.1% secondary fatty amines.

Example 16 16 grams of commercial Rufert catalyst (24.8% active nickel by weight) were extracted with butanol to remove the fat. The butanol was then replaced with absolute ethanol by several washlugs and decantations. After the final decantation, the ethanol wet paste was mixed with a small quantity of absolute ethanol so that. the total weight of ethanol was approximately 8 g, The resulting alcohol suspension was mixed with 400 g. of commercial stearic nitrile and 6.2 g. of ammonia in a 1 liter autoclave. Hydrogenation was conducted at a temperature of PEG-145 C. and a total pressure of 210 p. s. i. The catalyst was removed by filtration. Analysis of the resulting product showed 90.5% primary stearyl amine, 3.4% secondary stearyl amine, and approximately 6% of residue which could not be characterized.

Example 17 8 g. of water-wet commercial Raney nickel were washed with absolute ethanol, and the ethanol wet paste was mixed with 400 g. of commercial stearic nitrile. 40. g. of absolute ethanol were added and the mixture was charged to a 1 liter autoclave. 4.7 g. of ammonia were introduced at a temperature of 130 C. and the pressure at this stage was p. s. i. The hydrogenation was carried out at 140-145" C. and a total pressure of 200 p. s. i. The catalyst was removed by filtration. Analysis of the resulting product indicated 92.5% primary stearyl amine, 6.5% secondary stearyl amine, and 1% inert material. This example indicates that as much as 10% solvent may be employed, but that the increased concentration of solvent does not result in a significant increase in yield over the low concentration of solvent employed in most of the examples.

Example 1 8 400 grams of commercial stearic nitrile, 8 g. of cyclohexane, and 13 g. of reduced nickel borate catalyst were charged to a 1 liter autoclave. At C. 5.4 g. of ammonia were introduced to a total pressure of 84 p. s. i. The hydrogenation was then conducted at -145 C. and a total pressure of 230 p. s. i. When the hydrogenation was complete, the catalyst was removed by filtration. Analysis of the resulting product showed 84.5% primary stearyl amine, 15% of a. mixture of secondary and tertiary amine, and about 0.5% inert material.

Example 19 A reduced cobalt on Hyfio catalyst was prepared from 11 g. of a raw catalyst powder (U. S. Patent 2,166,183) by reduction in a hydrogen stream at 375 C. The reduced catalyst was poured into methanol and stirred. The catalyst was allowed to settle and the excess methanol was removed by decantation. The alcohol wet catalyst paste (containing about7-8 g. of methanol) was mixed with 400 g. of commercial stearic nitrile and charged to a 1 liter autoclave. The mixture was heated to about 132 C. with stirring, and gaseous ammonia was introduced until the equilibrium pressure was 76 p. s. i. (5.4 g. of ammonia). Hydrogen was then introduced to a total pressure of about 250 p. s. i. and the hydrogenation was completed at that pressure with a temperature of about -152 C. At the completion of the hydrogenation the catalyst was removed by filtration. Analysis of the resulting product showed 95.3% primary stearyl amine and 4.7 of residual material which was substantially secondary stearyl amine.

For comparison purposes, a similar hydrogenation was carried out in the absence of the solvent. The conditions were the same except that 5.5 g. of ammonia were employed, and the temperature was 145-160 C. during the hydrogenation. The product obtained contained 91.7 primary stearyl amine and 8.3% secondary stearyl amine.

While the examples have dealt largely with the hydrogenation of stearic nitrile, this has been primarily for the purpose of comparison of the various catalysts and the various solvents and other reaction conditions. The invention is equally applicable to other fatty nitriles within the range previously indicated. This is further indicated by the examples in which the crude nitriles from split brown grease or commercial tallow were hydrogenated.

' 9 We claim as our invention: 1. Process of hydrogenating fatty nitriles containing from 8 to 22 carbon atoms, which com,-

prises hydrogenating the nitriles in the presence of a hydrogenation catalyst, in th presence of ammonia employed in the ratio of from mol of ammonia per mol of nitrile, and in the presence of a low aliphatic alcohol, the alcohol being employed in the proportion of from -10% based on the weight of the nitrile.

2. Process of hydrogenating fatty nitriles con taining from 8 to 22 carbon atoms, which comprises preparing a mixture of a nickel hydrogenation catalyst, fatty nitrile, a low aliphatic alcohol, and ammonia, the alcohol being employed in the proportion from -10% based on the weight of the nitrile, and the ammonia being employed in the ratio of from A; to mol per mol of nitrile, subjecting the mixture to a temperature within the approximate range of 110-170" C. in the presence of hydrogen, the total pressure on the reaction mixture being at least 150 pounds per square inch.

3. Process of hydrogenating fatty nitriles containing from 8 to 22 carbon atoms, which comprises preparing a mixture containing th fatty nitrile, a low aliphatic alcohol in the proportion of from to 3% based on the weight of the fatty nitrile, ammonia in the proportion of from A; to /2 mol per mol of fatty nitrile, and a nickel hydrogenation catalyst, subjecting the mixture to a temperature of from 110-170 C. inthe presence of hydrogen under pressure, such that the total pressure on the reaction mixture is at least 150 pounds per square inch.

4. Process according to claim 3 in which the catalyst is a Raney nickel catalyst.

5. Process according to claim 3 in which the catalyst is a reduced nickel borate catalyst.

6. Process according to claim 3 in which the alcohol is methanol.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,160,578 Schmidt May 30, 1939 2,165,515 Schmidt July 11, 1939 FOREIGN PATENTS Number Country Date 282,083 Great Britain Nov, 8, 1928 536,940 Great Britain June 3, 1941 541,229 Germany Jan. 9, 1932 

2. PROCESS OF HYDROGENATING FATTY NITRILES CONTAINING FROM 8 TO 22 CARBON ATOMS, WHICH COMPRISES PREPARING A MIXTURE OF A NICKEL HYDROGENATION CATALYST, FATTY NITRILE A LOWER ALIPHATIC ALCOHOL, AND AMMONIA, THE ALCOHOL BEING EMPLOYED IN THE PROPORTION FROM 1/2-10% BASED ON THE WEIGHT OF THE NITRILE, AND THE AMMONIA BEING EMPLOYED IN THE RATIO OF FROM 1/4 TO 1/2 MOL PER MOL OF NITRILE, SUBJECTING THE MIXTURE TO A TEMPERATURE WITHIN THE APPROXIMATE RANGE OF 110-170* C. IN THE PRESENCE OF HYDROGEN, THE TOTAL PRESSURE ON THE REACTION MIXTURE BEING AT LEAST 150 POUNDS PER SQUARE INCH. 